Part of it may be our grudging acceptance of bad apples in the police system, like bad apples in organized religion and education. And unfortunately, police brutality has been around for millennia. Our modern police system has been modeled after London's 1829 police force, which they called the Peelers, Because they were organized by Sir Robert Peel. He was so concerned with introducing armed forces into the city and the backlash it may incite that he (1) disarmed the police, and (2) outfitted them in "blue" neutral colors, to make sure it looks nothing like the British red coats.